If such a device places a sheet on a stack against a mechanical stop, this sheet is released when deposited and, in this very moment, may bounce off said stop as a result of the impelling force applied to said sheet due to the rotation of the sheet transport element. This way of depositing a sheet, however, does not result in a neatly aligned stack. Therefore, the known device is operated such that, after the sheet has been deposited on the stack, said sheet is again pulled back against the stop by a drag element and, in so doing, is oriented and, in particular, aligned. This is particularly important if toner was applied to the sheet dining the printing process because, as a result of the application of toner to the sheet, said sheet may exhibit a varying overall thickness or a varying total material thickness, which, for example, causes the sheet to be systematically deposited on the stack in a wedge-shaped or curved manner, thus resulting in a corresponding leaning or buckling of the entire stack.
However, because the sheets are placed on a stack in potentially varying ways, the ultimate total height of the stack can be predicted only with difficulty, thus making the adjustment of the upper side to the correct level relative to the depositing device difficult; this, for example, could be accomplished by a stack depositing means which is lowered as the stack grows. Therefore, it must be taken into account that the drag element must overcome a greater height difference than expected, in which case a greater height difference also aids a sheet in bouncing off the stop. For example, a height difference of approximately only 2 to 3 mm could be desirable and, still, a height difference of, for example, approximately 15 mm or more could occur, in which case this height difference could additionally vary along a stop bar or a stack edge due to the wedging or buckling mentioned above.
Therefore, the object to be achieved by the present invention is to improve a device of the above-mentioned type in that at least one drag element is actuated at the right time at the right location.